But 9,000 children under the age of 15 in the U.S. are diagnosed with cancer each year, according to the American Cancer Society. Around 1,500 children die from cancer annually.

Chemical Hotspots

A study reported in the Journal of Epidemiology and Community Health included 22,500 children born between 1953 and 1980 who died from leukemia or other cancers before age 16.

Researchers pinpointed the locations of national chemical emissions "hotspots" from maps from the National Atmospheric Emissions Inventory (NAEI). The researchers looked at various chemicals from carbon monoxide to benzene.

They then calculated the distance between the hotspots and the child's birth address.

Findings dovetailed with those of earlier studies, which also seemed to indicate many childhood cancers probably start in early infancy or even earlier, in the womb. That would appear to have a direct correlation with how much exposure expectant mothers receive to toxic discharges into the atmosphere.

Bus Stations Carry Biggest Risk

According to the Occupational Safety and Health Administration, butadiene ranks in the top 10% of compounds most hazardous to humans and the environment. Three billion pounds are produced in the U.S. and 12 billion globally.

The biggest risk appeared to be to children living within 0.2 miles of a bus station. These children were 12 times more likely to die of cancer.

Other findings included:

Kids living within 0.2 miles of hospitals were more than twice as likely to die from cancer.

Kids living within 0.2 miles of heavy transport centers were nearly twice as likely to die from cancer.

Researchers say there is a specific association between childhood cancer and engine exhausts, especially diesel exhausts. They add that the chief cancer-causing substance is probably 1,3-butadiene.